Slot nozzles are used generally for various purposes for forming jets of gaseous or liquid fluid, for example onto a surface (eg. a moving fabric web or plate). Particular difficulties occur above all when the expelled flow medium is to be utilized to exert a high mechanical effect on a surface to be processed and in addition a relatively large working width is necessary with correspondingly large slot nozzle length.
Generally speaking, various nozzle designs are known in practice which comprise for example walls connected by screws or other connecting members and defining the slot, said walls being adjustable with respect to each other to obtain a definite slot width. To obtain a uniform nozzle effect it is further known to incorporate mechanical reinforcements in the interior of the nozzle. However, it has repeatedly been found in practice that a relative adjustment of the two walls defining the slot is comparatively complicated and expensive and that in addition the reinforcement fittings provided inside tend to promote the deposition of impurities and this can rapidly impair uniform operation of such a slot nozzle over its entire working length.
To extrude and cast foils, films or photographic emulsions an encased wide slot nozzle is also known (DE-OS No. 2, 022,415) in which the actual nozzle body is formed by two nozzle halves which enclose a cavity and define a nozzle slot with their longitudinal edges. The nozzle body formed from these two nozzle halves is suspended freely moveable within a separate housing. The drawings indicate moreover that the adjacent longitudinal sides of the two nozzle halves opposite the nozzle slot are merely pressed loosely against each other and permit a relative movement of the two longitudinal edges defining the slot. With such an embodiment it is however frequently difficult to control exactly the pressure acting in the outer surrounding chamber (the so-called compensation chamber) on the nozzle halves and thus in turn the particular slot width required.